Submicrosecond entangling gate between trapped ions via Rydberg interaction.

Generating quantum entanglement in large systems on timescales much shorter than the coherence time is key to powerful quantum simulation and computation. Trapped ions are among the most accurately controlled and best isolated quantum systems1 with low-error entanglement gates operated within tens of microseconds using the vibrational motion of few-ion crystals2,3. To exceed the level of complexity tractable by classical computers the main challenge is to realize fast entanglement operations in crystals made up of many ions (large ion crystals)4. The strong dipole-dipole interactions in polar molecule5 and Rydberg atom6,7 systems allow much faster entangling gates, yet stable state-independent confinement comparable with trapped ions needs to be demonstrated in these systems8. Here we combine the benefits of these approaches: we report a two-ion entangling gate with 700-nanosecond gate time that uses the strong dipolar interaction between trapped Rydberg ions, which we use to produce a Bell state with 78 per cent fidelity. The sources of gate error are identified and a total error of less than 0.2 per cent is predicted for experimentally achievable parameters. Furthermore, we predict that residual coupling to motional modes contributes an approximate gate error of 10-4 in a large ion crystal of 100 ions. This provides a way to speed up and scale up trapped-ion quantum computers and simulators substantially.

Real-imaginary spectrum decomposition of the transparency spectra in microwave dressed Rydberg systems.

To distinguish the contributions of electromagnetically induced transparency (EIT) and Autler-Townes splitting (ATS) in their applications in precision laser spectroscopy, we propose a real-imaginary spectrum decomposition method to investigate the transparency spectra in a four-level microwave (MW) dressed Rydberg system. We show that the opening transparency windows in the absorption spectra of probe field is a prominent character by EIT, EIT-ATS crossover, and ATS when the MW field is turned off and the intensity of the control field is adjusted. When the MW field is turned on and gradually increased, the EIT is destroyed and disappears. In addition, the most prominent characters that open a transparency window are the EIT-ATS crossover and the ATS. Then, if we further increase the intensity of the MW field, we find that the transparency windows open mainly due to the ATS. Compared to the previous considerations of this issue, which were limited to three-level systems, our four-level scheme reported here is useful for understanding the features of quantum interference in multilevel atomic systems, and has potential applications to study enhanced sensitivity, measurement spectroscopic, quantum processing, quantum communication, and transmission.

Spectral Signatures of Vibronic Coupling in Trapped Cold Ionic Rydberg Systems.

Atoms and ions confined with electric and optical fields form the basis of many current quantum simulation and computing platforms. When excited to high-lying Rydberg states, long-ranged dipole interactions emerge which strongly couple the electronic and vibrational degrees of freedom through state-dependent forces. This vibronic coupling and the ensuing hybridization of internal and external degrees of freedom manifest through clear signatures in the many-body spectrum. We illustrate this by considering the case of two trapped Rydberg ions, for which the interaction between the relative vibrations and Rydberg states realizes a quantum Rabi model. We proceed to demonstrate that the aforementioned hybridization can be probed by radio frequency spectroscopy and discuss observable spectral signatures at finite temperatures and for larger ion crystals.

Hb Guigang [α90 (FG2)Lys→Asn; HBA1:c.273G˃T]: a Novel α-Globin Chain Variant.

BACKGROUND: New hemoglobin (Hb) variants are constantly being updated as assays are developed and the testing population expands. Here, we report a novel Hb variant, named Hb Guigang. METHODS: Hemoglobin (Hb) analysis was analyzed by capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC). Glycated hemoglobin was performed by CE and HPLC. Routine genetic analysis was done with Gap-PCR and PCR-reverse dot-blot hybridization. The hemoglobin variant was identified by Sanger sequencing. RESULTS: CE of three cases showed the presence of Hb variants in Zone 5 and Zone 12, respectively. HPLC indicated an elevated P3 peak, suggesting the possible presence of the Hb variant. Hb A1c was measured by CE and HPLC, and the results were 6.7% and 4.76%, respectively. Sanger sequencing confirmed an AAG˃AAT mutation at codon 90 of the HBA1 gene. This mutation was reported for the first time, and we named it Hb Guigang based on the proband's place of residence. CONCLUSIONS: Hb Guigang with normal hematological parameters was separated and quantified by CE, whereas HPLC suggested that Hb Guigang co-eluted with the P3 peaks and could not be quantified.

Preliminary Study: 3D Nailing for Intertrochanteric Femur Fractures.

Objective: This study introduced the structural features of the Three-Dimensional Proximal Femoral Nail (3DPFN), a patented invention, and highlights its advantages in treating intertrochanteric fractures of the femur. Furthermore, biomechanical comparative experiments validated the biomechanical performance of 3DPFN in treating Evans-Jensen type IV intertrochanteric fractures. Methods: Evans-Jensen type IV intertrochanteric fracture models were created using artificial femurs produced by the American company Sawbone. From January to April 2022, the experimental group was fixed with 3DPFN, while the control group was fixed with the Proximal Femoral Nail Antirotation (PFNA), simulating the loading conditions in the human body. Axial static ultimate pressure tests and dynamic fatigue tests were conducted. The recorded parameters included the maximum load-bearing capacity under axial load, the maximum number of cycles, and the maximum load before failure. Results: Static ultimate pressure tests showed that the static ultimate load in the 3DPFN group was 2532.67±49.20N, whereas in the PFNA group, it was 2240.00±84.35N, with a significant difference between the two groups (P < .05). Dynamic fatigue tests revealed that the maximum number of cycles in the 3DPFN group was 86372.67±4762.59 cycles, while in the PFNA group, it was 8606.67±606.05 cycles, also showing a significant difference (P < .05). Dynamic fatigue tests further indicated that the fatigue limit load before failure in the 3DPFN group was 1664.00±78.27N, whereas in the PFNA group, it was 799.33±63.52N. Again, there was a significant difference between the two groups (P < .05). Conclusion: In both static compression and fatigue tests, 3DPFN exhibits significant biomechanical advantages over PFNA. This suggests that 3DPFN may be an excellent choice for the treatment of intertrochanteric fractures of the femur and holds further research value for development. Future studies may involve clinical trials to validate and refine the 3DPFN design based on the observed results and promote the advancement of orthopedic implant technology.

Predictive Model Construction And Prevention Strategies Of Surgical Site Infection In Laparoscopic Appendectomy.

Objective: To construct a nomogram model for predicting the occurrence of the laparoscopic appendectomy surgical site infection (LASSI) and explore prevention strategies. Methods: A total of 995 patients who underwent laparoscopic appendectomy in Shanxi Bethune Hospital from October 2017 to August 2022 were selected. According to whether there was incision infection within 30 days after operation, the patients were divided into the LASSI (97 cases) and non-LASSI (898 cases) group. The following clinicopathological data from these two groups of patients were collected: gender, age, body mass index, ect. The subjects were randomly divided into training group and verification group according to the 7:3 ratio. Univariate and multivariate analysis was used to screen the related influencing factors and construct a nomogram model to predict the occurrence of LASSI. Rreceiver operating characteristic (ROC) curves and the calibration curve were used to evaluate the predictive value of the model. For patients with LASSI, a more effective preventive measure was explored. Results: Multivariate logistic regression analysis showed that operation time >1h (OR: 1.891; 95% CI: 1.07 to 3.36; P = .029), perforated and gangrenous appendix (OR: 4.078; 95% CI: 1.84 to 9.86; P = .001), free intraperitoneal fluid (OR: 2.836; 95% CI: 1.57 to 5.35; P = .001), BMI>30 kg/m2 (OR: 2.828; 95% CI:1.54 to 5.12; P = .001), diabetes mellitus (DM) (OR: 2.795; 95% CI: 1.54 to 5.28; P = .001) were the independent prognostic factors of LASSI. The prediction nomogram model showed satisfactory performance in predicting the occurrence of LASSI, ROC curve area value of the training and verification groups were respectively 0.753 (95 % CI: 0.688 ~ 0.818) and 0.772 (95 % CI: 0.691-0.852). In the event of LASSI, we took out appendix specimens in sections and sterilized surgical site, which effectively prevented it. Conclusion: This study evaluated the risk factors related to the occurrence of LASSI and established a prediction model for LASSI. The prediction model provides a convenient and fast risk assessment tool for clinicians to predict the occurrence of LASSI. Combined with the newly discovered prevention strategy of segmental removal of appendix and incision disinfection, it can effectively avoid the occurrence of LASSI and potentially reduce the hospitalization time and costs.

Hb Hebei [α20 (B1) His→Leu; HBA2:C.62A > T]: A Novel Hemoglobin Variant Found during Measurement of Glycated Hemoglobin.

We report a novel hemoglobin (Hb) variant found in a 34-year-old Chinese male during a routine measurement of glycated hemoglobin. The variant resulted in a P3 peak of 27.5% of the total Hb on high performance liquid chromatography (HPLC) with a glycated hemoglobin mode. However, no abnormal Hb peaks were observed in capillary electrophoresis (CE) with 3.1% Hb A2 and 96.9% Hb A. The amino acid substitution was determined by Sanger sequencing as α20 (B1) His→Leu; the corresponding DNA mutation was identified as CAC > CTC at the first position of codon 20 of the α-chain. This is the first description of the mutation, and we have named it Hb Hebei for the region of origin of the proband.

Enhanced Electrochemiluminescence of Luminol and-Dissolved Oxygen by Nanochannel-Confined Au Nanomaterials for Sensitive Immunoassay of Carcinoembryonic Antigen.

Simple development of an electrochemiluminescence (ECL) immunosensor for convenient detection of tumor biomarker is of great significance for early cancer diagnosis, treatment evaluation, and improving patient survival rates and quality of life. In this work, an immunosensor is demonstrated based on an enhanced ECL signal boosted by nanochannel-confined Au nanomaterial, which enables sensitive detection of the tumor biomarker-carcinoembryonic antigen (CEA). Vertically-ordered mesoporous silica film (VMSF) with a nanochannel array and amine groups was rapidly grown on a simple and low-cost indium tin oxide (ITO) electrode using the electrochemically assisted self-assembly (EASA) method. Au nanomaterials were confined in situ on the VMSF through electrodeposition, which catalyzed both the conversion of dissolved oxygen (O2) to reactive oxygen species (ROS) and the oxidation of a luminol emitter and improved the electrode active surface. The ECL signal was enhanced fivefold after Au nanomaterial deposition. The recognitive interface was fabricated by covalent immobilization of the CEA antibody on the outer surface of the VMSF, followed with the blocking of non-specific binding sites. In the presence of CEA, the formed immunocomplex reduced the diffusion of the luminol emitter, resulting in the reduction of the ECL signal. Based on this mechanism, the constructed immunosensor was able to provide sensitive detection of CEA ranging from 1 pg·mL-1 to 100 ng·mL-1 with a low limit of detection (LOD, 0.37 pg·mL-1, S/N = 3). The developed immunosensor exhibited high selectivity and good stability. ECL determination of CEA in fetal bovine serum was achieved.

Preoperative versus postoperative nonsteroidal anti-inflammatory drugs in femoroacetabular impingement patients undergoing hip arthroscopy surgery: analgesic effect, joint function, patients' satisfaction, and quality of life.

BACKGROUND: Nonsteroidal anti-inflammatory drugs (NSAIDs) have analgesic effects on femoroacetabular impingement (FAI) patients undergoing hip arthroscopy surgery (HAS). However, the influence of medication time on the analgesic effect of NSAIDs is uncertain. This study aimed to compare the analgesic effect, joint function, quality of life (QoL), and patients' satisfaction between preoperative and postoperative NSAIDs in these patients. METHODS: In this prospective, observational study, 165 FAI patients undergoing HAS with NSAIDs (celecoxib, meloxicam, and nimesulide) for analgesia were divided into preoperative (PRE-A) and postoperative analgesia (POST-A) groups according to their actual medication. RESULTS: The visual analog scale (VAS) pain scores on the 1st (P < 0.001) and 3rd (D3) (P = 0.015) days after the operation were lower in the PRE-A group versus the POST-A group but not preoperatively (P = 0.262) or on the 7th day after the operation (D7) (P = 0.302). The proportion of patients receiving rescue analgesia decreased in the PRE-A group versus POST-A group (P = 0.041). However, the modified Harris hip score (mHHS), proportion of patients with an mHHS ≥ 70, and EuroQol-5-dimensional score at preoperative, 1st month (M1), and 3rd month (M3) after the operation were similar between the groups (all P > 0.050). The VAS score on D7 was greater in the PRE-A group compared to the POST-A group (P = 0.014), but the scores at M1 and M3 and the satisfaction and very satisfaction rates at D7, M1, and M3 did not differ between the groups (all P > 0.050). Subgroup analysis revealed that the type of NSAID did not affect most outcomes. CONCLUSION: Preoperative NSAIDs elevate analgesic effect and patients' satisfaction, but not joint function or QoL compared to postoperative NSAIDs in FAI patients undergoing HAS.

Quantum sensing of microwave electric fields based on Rydberg atoms.

Microwave electric field (MW E-field) sensing is important for a wide range of applications in the areas of remote sensing, radar astronomy and communications. Over the past decade, Rydberg atoms have been used in ultrasensitive, wide broadband, traceable, stealthy MW E-field sensing because of their exaggerated response to MW E-fields, plentiful optional energy levels and integratable preparation methods. This review first introduces the basic concepts of quantum sensing, the properties of Rydberg atoms and the principles of quantum sensing of MW E-fields with Rydberg atoms. An overview of this very active research direction is gradually expanding, covering the progress of sensitivity and bandwidth in Rydberg atom-based microwave sensing, superheterodyne quantum sensing with microwave-dressed Rydberg atoms, quantum-enhanced sensing of MW E-field and recent advanced quantum measurement systems and approaches to further improve the performance of MW E-field sensing. Finally, a brief outlook on future development directions is provided.

Modeling the mechanisms of conifer mortality under seawater exposure.

Relative sea level rise (SLR) increasingly impacts coastal ecosystems through the formation of ghost forests. To predict the future of coastal ecosystems under SLR and changing climate, it is important to understand the physiological mechanisms underlying coastal tree mortality and to integrate this knowledge into dynamic vegetation models. We incorporate the physiological effect of salinity and hypoxia in a dynamic vegetation model in the Earth system land model, and used the model to investigate the mechanisms of mortality of conifer forests on the west and east coast sites of USA, where trees experience different form of sea water exposure. Simulations suggest similar physiological mechanisms can result in different mortality patterns. At the east coast site that experienced severe increases in seawater exposure, trees loose photosynthetic capacity and roots rapidly, and both storage carbon and hydraulic conductance decrease significantly within a year. Over time, further consumption of storage carbon that leads to carbon starvation dominates mortality. At the west coast site that gradually exposed to seawater through SLR, hydraulic failure dominates mortality because root loss impacts on conductance are greater than the degree of storage carbon depletion. Measurements and modeling focused on understanding the physiological mechanisms of mortality is critical to reducing predictive uncertainty.

Controllable bistability and squeezing of confined polariton dark solitons.

The generation of squeezed light in semiconductor materials opens opportunities for building on-chip devices that are operated at the quantum level. Here we study theoretically a squeezed light source of polariton dark solitons confined in a geometric potential well of semiconductor microcavities in the strong coupling regime. We show that polariton dark solitons of odd and even parities can be created by tuning the potential depth. When driving the potential depth linearly, a bistability of solitons with the two different parities can be induced. Strong intensity squeezing is obtained near the turning point of the bistability due to the large nonlinear interaction, which can be controlled by the cavity detuning. The phase diagram of the bistability and squeezing of the dark solitons is obtained through large scale numerical calculations. Our study contributes to the current efforts in realizing topological excitations and squeezed light sources with solid-state devices.

Dephasing of ultracold cesium 80D5/2-Rydberg electromagnetically induced transparency.

We study Rydberg electromagnetically induced transparency (EIT) of a cascade three-level atom involving 80D5/2 state in a strong interaction regime employing a cesium ultracold cloud. In our experiment, a strong coupling laser couples 6P3/2 to 80D5/2 transition, while a weak probe, driving 6S1/2 to 6P3/2 transition, probes the coupling induced EIT signal. At the two-photon resonance, we observe that the EIT transmission decreases slowly with time, which is a signature of interaction induced metastability. The dephasing rate γOD is extracted with optical depth OD = γODt. We find that the optical depth linearly increases with time at onset for a fixed probe incident photon number Rin before saturation. The dephasing rate shows a nonlinear dependence on Rin. The dephasing mechanism is mainly attributed to the strong dipole-dipole interactions, which leads to state transfer from nD5/2 to other Rydberg states. We demonstrate that the typical transfer time τ0(80D) obtained by the state selective field ionization technique is comparable with the decay time of EIT transmission τ0(EIT). The presented experiment provides a useful tool for investigating the strong nonlinear optical effects and metastable state in Rydberg many-body systems.

The influence of increasing atmospheric CO2 , temperature, and vapor pressure deficit on seawater-induced tree mortality.

Increasing seawater exposure is killing coastal trees globally, with expectations of accelerating mortality with rising sea levels. However, the impact of concomitant changes in atmospheric CO2 concentration, temperature, and vapor pressure deficit (VPD) on seawater-induced tree mortality is uncertain. We examined the mechanisms of seawater-induced mortality under varying climate scenarios using a photosynthetic gain and hydraulic cost optimization model validated against observations in a mature stand of Sitka spruce (Picea sitchensis) trees in the Pacific Northwest, USA, that were dying from recent seawater exposure. The simulations matched well with observations of photosynthesis, transpiration, nonstructural carbohydrates concentrations, leaf water potential, the percentage loss of xylem conductivity, and stand-level mortality rates. The simulations suggest that seawater-induced mortality could decrease by c. 16.7% with increasing atmospheric CO2 levels due to reduced risk of carbon starvation. Conversely, rising VPD could increase mortality by c. 5.6% because of increasing risk of hydraulic failure. Across all scenarios, seawater-induced mortality was driven by hydraulic failure in the first 2 yr after seawater exposure began, with carbon starvation becoming more important in subsequent years. Changing CO2 and climate appear unlikely to have a significant impact on coastal tree mortality under rising sea levels.

Seawater exposure causes hydraulic damage in dying Sitka-spruce trees.

Sea-level rise is one of the most critical challenges facing coastal ecosystems under climate change. Observations of elevated tree mortality in global coastal forests are increasing, but important knowledge gaps persist concerning the mechanism of salinity stress-induced nonhalophytic tree mortality. We monitored progressive mortality and associated gas exchange and hydraulic shifts in Sitka-spruce (Picea sitchensis) trees located within a salinity gradient under an ecosystem-scale change of seawater exposure in Washington State, USA. Percentage of live foliated crown (PLFC) decreased and tree mortality increased with increasing soil salinity during the study period. A strong reduction in gas exchange and xylem hydraulic conductivity (Ks) occurred during tree death, with an increase in the percentage loss of conductivity (PLC) and turgor loss point (πtlp). Hydraulic and osmotic shifts reflected that hydraulic function declined from seawater exposure, and dying trees were unable to support osmotic adjustment. Constrained gas exchange was strongly related to hydraulic damage at both stem and leaf levels. Significant correlations between foliar sodium (Na+) concentration and gas exchange and key hydraulic parameters (Ks, PLC, and πtlp) suggest that cellular injury related to the toxic effects of ion accumulation impacted the physiology of these dying trees. This study provides evidence of toxic effects on the cellular function that manifests in all aspects of plant functioning, leading to unfavourable osmotic and hydraulic conditions.

Chemokine CXCL1 as a potential marker of disease activity in systemic lupus erythematosus.

OBJECTIVES: The chemokine CXCL1, known as growth-related oncogene α (GRO-α), is a potent chemoattractant and regulator of neutrophils. The purpose of our study was to evaluate the regulatory response of CXCL1 in the serum of patients with systemic lupus erythematosus (SLE) in the active stage of disease and to assess whether it was implicated in the pathogenesis/inflammatory process in lupus. METHODS: CXCL1 serum concentrations were examined in 90 SLE patients, 56 other autoimmune diseases (OADs) patients and 100 healthy controls using enzyme-linked immunosorbent methodology. RESULTS: SLE patients exhibited significant increases in serum CXCL1 concentrations [1492.86 (735.47-2887.34) pg/ml] compared with OADs patients [155.88 (10.77-366.78) pg/ml] and healthy controls [13.58 (8.46-37.22) pg/ml] (p < 0.001). Moreover, the level of CXCL1 decreased as the level of anti-dsDNA IgG decreased after treatment between the anti-dsDNA-positive SLE patients and the anti-dsDNA-negative SLE patients. Additionly, serum CXCL1 concentrations were related to different disease activity levels in SLE and lupus nephritis (LN) and high avidity of IgG ANAs (HA IgG ANAs) (p < 0.05). Furthermore, CXCL1 serum concentrations were significantly correlated with the SLE Disease Activity Index(SLEDAI) score, relative avidity index (RAI) of HA IgG ANAs and the levels of anti-dsDNA IgG, CRP, ESR, albumin, C3 and C4.Additionally, Statistical analysis revealed that positivity for IgG ANA (p < 0.001), the presence of HA IgG ANAs (p = 0.001) and the logarithmic level of anti-dsDNA IgG (p = 0.021) were significantly associated with the logarithmic level of CXCL1 with standard partial regression coefficients (95% CI) of 2.371 (1.734-3.009), 1.231 (0.52-1.937) and 0.409 (0.062-0.755), respectively. Finally, using cutoff points of 1182.17 pg/mL and 1500.31 pg/mL, serum CXCL1 levels had a similar sensitivity of 76% and specificity of 100% and 75% for the diagnosis of active SLE and LN, respectively. CONCLUSIONS: Serum CXCL13 concentrations might represent a potential marker of disease activity in systemic lupus erythematosus.

Stability of tropical forest tree carbon-water relations in a rainfall exclusion treatment through shifts in effective water uptake depth.

Increasing severity and frequency of drought is predicted for large portions of the terrestrial biosphere, with major impacts already documented in wet tropical forests. Using a 4-year rainfall exclusion experiment in the Daintree Rainforest in northeast Australia, we examined canopy tree responses to reduced precipitation and soil water availability by quantifying seasonal changes in plant hydraulic and carbon traits for 11 tree species between control and drought treatments. Even with reduced soil volumetric water content in the upper 1 m of soil in the drought treatment, we found no significant difference between treatments for predawn and midday leaf water potential, photosynthesis, stomatal conductance, foliar stable carbon isotope composition, leaf mass per area, turgor loss point, xylem vessel anatomy, or leaf and stem nonstructural carbohydrates. While empirical measurements of aboveground traits revealed homeostatic maintenance of plant water status and traits in response to reduced soil moisture, modeled belowground dynamics revealed that trees in the drought treatment shifted the depth from which water was acquired to deeper soil layers. These findings reveal that belowground acclimation of tree water uptake depth may buffer tropical rainforests from more severe droughts that may arise in future with climate change.

Exploring the Many-Body Dynamics Near a Conical Intersection with Trapped Rydberg Ions.

Conical intersections between electronic potential energy surfaces are paradigmatic for the study of nonadiabatic processes in the excited states of large molecules. However, since the corresponding dynamics occurs on a femtosecond timescale, their investigation remains challenging and requires ultrafast spectroscopy techniques. We demonstrate that trapped Rydberg ions are a platform to engineer conical intersections and to simulate their ensuing dynamics on larger length scales and timescales of the order of nanometers and microseconds, respectively; all this in a highly controllable system. Here, the shape of the potential energy surfaces and the position of the conical intersection can be tuned thanks to the interplay between the high polarizability and the strong dipolar exchange interactions of Rydberg ions. We study how the presence of a conical intersection affects both the nuclear and electronic dynamics demonstrating, in particular, how it results in the inhibition of the nuclear motion. These effects can be monitored in real time via a direct spectroscopic measurement of the electronic populations in a state-of-the-art experimental setup.

Magnetic Hysteresis in a Monolayer of Oriented 6 nm CsNiCr Prussian Blue Analogue Nanocrystals.

Prussian blue analogue nanocrystals of the CsINiII[CrIII(CN)6] cubic network with 6 nm size were assembled as a single monolayer on highly organized pyrolytic graphite (HOPG). X-ray magnetic circular dichroism (XMCD) studies, at the Ni and Cr L2,3 edges, reveal the presence of an easy plane of magnetization evidenced by an opening of the magnetic hysteresis loop (coercive field of ≈200 Oe) when the magnetic field, B, is at 60° relative to the normal to the substrate. The angular dependence of the X-ray natural linear dichroism (XNLD) reveals both an orientation of the nanocrystals on the substrate and an anisotropy of the electronic cloud of the NiII and CrIII coordination sphere species belonging to the nanocrystals' surface. Ligand field multiplet (LFM) calculations that reproduce the experimental data are consistent with an elongated tetragonal distortion of surface NiII coordination sphere responsible for the magnetic behavior of monolayer.

Detection and Location of Surface Damage Using Third-Order Combined Harmonic Waves Generated by Non-Collinear Ultrasonic Waves Mixing.

Metals which are widely used in many types of industries are usually subjected to fatigue and surface corrosion. There is a demand to detect the surface damage caused by fatigue and corrosion at an early stage to ensure the structural integrity. In this paper, a novel nonlinear ultrasonic technique based on the measure of third-order combined harmonic generation, is proposed to detect and locate the surface damage in 6061 aluminum alloy. Third-order combined harmonic generation caused by non-collinear mixing of one longitudinal wave and one transverse wave at different frequencies, is firstly analyzed and experimentally observed. An experimental procedure of nonlinear scanning is proposed for the damage detection and location by checking the variation of frequency nonlinear response. The correlations of nonlinear frequency mixing responses and surface damage in the specimens are obtained. Results show that the nonlinear response caused by fatigue damage and surface corrosion can be identified and located by this method. In addition, this approach can exclude the nonlinearity induced by the instruments and simplify the signal processing.